LTC1289 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1289' PDF : 28 Pages View PDF
LTC1289
TYPICAL APPLICATI S
SNEAK-A-BITTM
The LTC1289’s unique ability to software select the polar-
ity of the differential inputs and the output word length is
used to achieve one more bit of resolution. Using the
circuit below with two conversions and some software, a
2’s complement 12-bit + sign word is returned to memory
inside the MPU. The MC68HC05C4 was chosen as an
example, however, any processor that operates at 3.3V
could be used.
Two 12-bit unipolar conversions are performed: the first
over a 0V to 2.5V span and the second over a 0V to –2.5V
span (by reversing the polarity of the inputs). The sign of
the input is determined by which of the two spans con-
tained it. Then the resulting number (ranging from –4095
to +4095 decimal) is converted to 2’s complement nota-
tion and stored in RAM.
SNEAK-A-BIT Circuit
22µF
+3.3V
2MHz
ACLK
OTHER CHANNELS
OR SNEAK-A-BIT
INPUTS
VIN
–2.5V TO +2.5V
CHO
VCC
CH1
ACLK
CH2
SCLK
CH3
DIN
CH4
DOUT
LTC1289
CH5
CS
CH6
REF+
CH7
REF–
COM
V–
DGND
AGND
1k
10µF
LT1019
–2.5
0.1µF
–3.3V
MC68HC05C4
SCLK
MOSI
MISO
CO
LTC1289 TA03
SNEAK-A-BIT
2.5V
VIN
(+) CH6
(–) CH7
1ST CONVERSION
0V
VIN
2.5V
1ST CONVERSION
4096 STEPS
SOFTWARE
0V
0V
(–) CH6
(+) CH7
2ND CONVERSION
–2.5V
2ND CONVERSION
4096 STEPS
–2.5V
8191 STEPS
LTC1289 TA04
SNEAK-A-BIT is a trademark of Linear Technology Corp.
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